Cylindrical roller bearing comprises three major sections. The foremost would be the inner bearing race that fits comfortably on the turning shaft, or could be the hard enough shaft metal. The second could be the outer race forms a uniform and hard collar fitting easily inside the bearing holder bore.
The third could be adequate number of uniform straight rollers to fill the space between the two races without biding them together. It would be pertinent to mention here that the bearings would last nearly forever when sealed, has been kept relatively clean, and lubricated with high film strength-bearing grease.